Field of the Invention
The present invention relates to a method for manufacturing a transdermal-absorption sheet, and in particular, to a technique for concentrating a drug at needle-like protruding portions.
Description of the Related Art
In recent years, a method has been carried out in which a chemical is injected by using a transdermal-absorption sheet provided with needle-like protruding portions having a high aspect ratio and containing a drug to insert the needle-like protruding portions into the skin. In order to allow the transdermal-absorption sheet to be used as a drug, the drug needs to be mixed into the sheet. Many drugs are expensive, and thus, the drug needs to be contained in the sheet so as to concentrate at the needle-like protruding portions.
As a method for manufacturing a transdermal-absorption sheet, a method is known in which a polymer solution or the like is poured into a mold on which needle-like recessed portions that are inverted shapes of needle-like protruding portions are formed, to transfer the shapes. For example, Japanese Patent Application Laid-Open No. 2011-078617 (PTL 1) discloses use of a stamper for microneedle sheets in which through-holes penetrating a parent material are made at the bottoms of the recessed portions. PTL 1 discloses a method of first coating a surface of the stamper with a solution of a diluted drug, subsequently scraping off extra solution using a squeegee or the like, drying the drug solution, and then coating the dried drug solution with a needle raw material.
Furthermore, Japanese Patent Application Laid-Open No. 2009-195583 (PTL 2) discloses a method for manufacturing a sheet in which microneedle-like protrusions are accumulated. In the method, the sheet can be accurately manufactured in one step by filling a flexible substrate with a thick liquid consisting of a mixture of a target substance and a base utilizing a centrifugal force, while drying and hardening the liquid.